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Gypsum hemihydrate Monohydrate gypsum and dihydrate gypsum

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Gypsum hemihydrate Monohydrate gypsum and dihydrate gypsum

(PDF) Dehydration Pathways of Gypsum and the Rehydration Mechanism …

Part I. Kinetics of dehydration of calcium sulphate dihydrate. J. ... 2020) over bassanite (hemihydrate; CaSO4•0.5H2O) to gypsum (CaSO4•2 H2O), accompanied with a volume increase of ~61 % ...

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Preparation of Whitening Dihydrate Gypsum and Short …

Using FGD gypsum as the raw material, whitening and large prismatic dihydrate gypsum can be obtained by dissolution‐crystallization and decoloring process with α‐hemihydrate gypsum whiskers prepared in MgSO4‐CaCl2‐H2O solution, which can transform into whitening short columnar α‐hemihydrate gypsum. The effects of aging …

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The dihydrate‐hemihydrate transformation in gypsum

Download Citation | The dihydrate‐hemihydrate transformation in gypsum | A microscope study has been made of the development of crystals of calcium sulphate hemihydrate produced on, or in ...

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Aspects of gypsum dihydrate crystallization in the artificial …

The present paper investigates aspects of the crystallization of gypsum dihydrate during the artificial "aging" of calcined gypsum binder. ... in producing gypsum binders has received a great deal of attention in recent years owing to the instability of calcined gypsum properties [1]. Gypsum hemihydrate is a material used in the building ...

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Calcium Sulfate Hemihydrate

Calcium Sulfate Hemihydrate, also known as plaster of Paris, is a material made from gypsum that has been used for centuries in construction and various medical …

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Synthesis and Characterisation of Hemihydrate Gypsum…

This study combined inorganic α-hemihydrate gypsum (α-HHG) with organic polyacrylamide (PAM) hydrogel to create a novel α-HHG/PAM composite material. Through this facile composite strategy, this fabricated material exhibited a significantly longer initial setting time and higher mechanical strength compared to α-HHG. The …

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The thermal dehydration of natural gypsum and pure calcium sulphate

thermochimica acta ELSEVIER Thermochimica Acta 282/283 (1996) 483-492 The thermal dehydration of natural gypsum and pure calcium sulphate dihydrate (gypsum)' D.L. Hudson-Lamb", C.A. Strydom a, J.H. Potgieter b a Department oJ'Chemistry, University of Pretoria, Pretoria, 0002, South Africa b Technical Services, …

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Formation of α-Hemihydrate Inside of a Gypsum Crystal …

Figure 7. Gypsum crystal partly dehydrated, cleaved along cleavage plane, with observable dihydrate, α β α-hemihydrate and β-hemihydrate. Yellow circle = still dihydrate, blue circle = alpha hemihydrate, red circle = beta hemihydrate, black arrow = alpha hemihydrate growing direction of a needle like crystal.

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Effect of Fluorine and Phosphorus Impurities in …

In this study, phosphogypsum (PG) is simulated by doping fluorine and phosphorus ions in an analytically pure reagent of gypsum dihydrate. The influence of fluorine and phosphorus impurity and content on the dehydration reaction process of phosphogypsum and its crystalline micromorphology is assessed during the preparation …

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Effect of modifiers on crystalizing habit and mechanical …

Effects of modifiers on growth of α-hemihydrate gypsum were examined. • Crystallisation habit of α-hemihydrate gypsum was studied by XRD, XPS and simulation. • Interaction energies between additives and crystal planes were gained by simulation. • The modifiers significantly increased the strength of α-hemihydrate gypsum.

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Fast in-situ X-ray scattering reveals stress sensitivity of gypsum

The calcium sulphate dihydrate gypsum (CaSO 4 ·2H 2 O) is the most common sulphate evaporite mineral on our planet 1.Sulphate evaporites play an important role in Earth's sulphur cycle and are ...

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A new Precipitation Pathway for Calcium Sulfate Dihydrate (Gypsum…

The mechanism of the nonclassical crystallization pathway of calcium sulfate dihydrate (gypsum) with calcium sulfate hemihydrate (bassanite) as a precursor has been considered in many studies.

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Eco-friendly, high-toughness gypsum prepared using hemihydrate

1. Introduction. Phosphogypsum (PG), an industrial byproduct of wet-process phosphoric acid production, is mainly composed of calcium sulfate dihydrate (CaSO 4 · 2H 2 O). According to statistics, each ton of phosphate fertilizer will yield approximately five tons of PG [1].China is among the largest PG producers worldwide, with a cumulative …

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USG Gypsum Misconceptions White Paper (English)

Ground gypsum in and by itself will not get hard when mixed with water. Gypsum has to be converted to a "hemihydrate" by first cooking it. The process of cooking gypsum is called …

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Calcium Sulphate Hemihydrate Hydration Leading to Gypsum

The hydration of calcium sulphate hemihydrate (CaSO4·0.5H2O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO4·2H2O) has been the subject of several investigations ...

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Understanding gypsum in 3 diagrams

There are three main diagrams that can help us understand this cycle in detail. The first describes the process of water leaving the structure of gypsum to form …

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Reuse of Gypsum Hemihydrate: Effect of Different …

Abstract. This study investigates the viability of employing various retardants, namely wheat hydrolyzed protein (GEM), sodium carboxymethyl cellulose (CMC-Na), inorganic retarders such as borax (PS), and sodium tripolyphosphate (STPP), to serve as multifaceted retarding agents for calcined 180°C β-hemihydrate gypsum (β-HH).The …

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Calcium sulphate hemihydrate hydration leading to gypsum

This article focuses on the hydration, and associated microstructure development, of β-hemihydrate to dihydrate (gypsum). The sound velocity is used to quantify the composition of the fresh slurry as … Expand. 5. PDF. Save. Preparation of α-Calcium Sulfate Hemihydrate from Phosphogypsum in CaCl2 Solution under …

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Gypsum hemihydrate–cement blends to improve …

CaSO4 þ 2H2 O Gypsum ð1Þ b-hemihydrate ð3Þ Anhydrite II Both b-hemihydrate and anhydrite III at normal temperature react with water forming dihydrate (gypsum). This reaction makes a network of gypsum crystals that produces the properties of gypsum-based materials.

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Crystallization of gypsum from hemihydrate in presence of …

The crystallization of gypsum (CaSO 4 ·2H 2 O) from a suspension of calcium sulphate hemihydrate is well-known as the setting of plaster. In this paper we present results concerning the crystallization of gypsum in the presence of different acids. ... The three different stages, observed in Fig. 1, correspond to the hemihydrate …

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Autoclave‐Free Formation of α‐Hemihydrate Gypsum

On comparing the solubility of calcium sulfate dihydrate and α-calcium sulfate hemihydrate in the formamide aqueous solution, it was found that the solubility of α-calcium sulfate hemihydrate is ...

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Formation of α-Hemihydrate Inside of a Gypsum Crystal …

Gypsum crystal partly dehydrated, cleaved along cleavage plane, with observable dihydrate, α-hemihydrate and β-hemihydrate. Yellow circle = still dihydrate, blue circle = alpha hemihydrate, red ...

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Influence of calcination and GGBS addition in preparing β-hemihydrate …

This is because the main composition of PG is dihydrate gypsum (CaSO 4 ⋅2H 2 O), which can be dehydrated to form synthetic hemihydrate gypsum, like natural mineral gypsum. Depending on the temperature and condition of the dehydration process, natural gypsum exists in four different phases, namely hemihydrate gypsum (CaSO 4 …

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What is the Difference Between Alpha and Beta Hemihydrate

The process of converting gypsum into alpha hemihydrate involves heating gypsum at a specific temperature to remove water molecules, resulting in a more concentrated and stable form of calcium sulfate. ... The main difference between calcium sulfate dihydrate and hemihydrate is their water content. Calcium sulfate dihydrate …

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Gypsum hydration: a theoretical and experimental study

consumption of hemihydrate and formation of dihydrate. 1. Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first stage and the nucleation and precipitation of dihydrate in the second stage. 2. Gypsum hydration is strongly influenced by water amount. Spread flow test is

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Gypsum: an old product with a new use | Integrated Crop …

Gypsum is calcium sulfate (CaSO 4).Refined gypsum in the anhydrite form (no water) is 29.4 percent calcium (Ca) and 23.5 percent sulfur (S). Usually, gypsum has water associated in the molecular structure (CaSO 4 ·2H2O) and is approximately 23.3 percent Ca and 18.5 percent S (plaster of paris). Gypsum fertilizer usually has other impurities …

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Gypsum Products

Gypsum mineral content in the sedimentary rock termed gypsum varies from 75% to 95%, the rest being formed of chalk and/or clay. The chemical name of gypsum is calcium …

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Transformation of Flue-Gas-Desulfurization Gypsum to (α …

Further research into FGD gypsum is thus necessary. Utilization of FGD gypsum depends on whether it can be transformed into various products in the form of calcium sulfate dihydrate (DH), calcium sulfate hemihydrate (D- and E-HH) or calcium sulfate anhy- drate (AH).

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Influencing the Morphology of Gypsum | SpringerLink

Gypsum (calcium sulfate dihydrate) is burned to calcium sulfate hemihydrates or anhydrite to be used in different building materials. The hemihydrate and anhydrite …

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Insight into the influences of β-hemihydrate and dihydrate gypsum …

It is still uncertain whether β-hemihydrate and dihydrate gypsum influence the properties, especially the phase conversion, of white calcium aluminate cement (CAC). Therefore, in this study, we prepared CAC pastes/mortars containing β-hemihydrate and dihydrate and comparatively assessed their setting times and compressive strengths ...

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